I
G
j B
V
I
j I
o stab
ostab
ostab
baseres
oCosstab
oSinsta
1
1
1
1
=
+ ⋅
⋅
=
+ ⋅
(
)
b
b
1
GUID-0D93E27A-4B7A-4166-928B-40E7EEED0CDE V1 EN
(Equation 64)
I
o stab
1
The stabilized fundamental frequency residual current estimate, which is obtained (after
conversion) from the corresponding admittance value by multiplying it with the system nominal
phase-to-ground voltage value.
I
o Cosstab
1
The real-part of stabilized fundamental frequency residual current estimate.
I
o Sinstab
1
The imaginary-part of stabilized fundamental frequency residual current estimate.
The main advantage of the filtering method is that due to the admittance calculation, the
resulting current value does not depend on the value of fault resistance, that is, the
estimated current magnitude equals the value that would be measured during a solid
ground fault (R
f
= 0 Ω). Another advantage of the method is that it is capable of estimating
correct current magnitude also during intermittent or restriking faults.
The setting
Min trip current
defines the minimum trip current.
Setting
Operating quantity
defines whether the current magnitude supervision is based on
either the “Adaptive” or “Amplitude” methods.
When “Adaptive” is selected, the method adapts the principle of magnitude supervision
automatically to the system grounding condition. In case the phase angle of accumulated
sum admittance phasor is greater than 45 degrees, the set minimum trip current threshold
is compared to the amplitude of
I
o stab
1
). In case the phase angle of
accumulated sum admittance phasor is below 45 degrees, the set minimum trip current
threshold is compared to the resistive component of
I
o stab
1
. This automatic adaptation of
the magnitude supervision enables secure and dependable directional determination in
compensated networks, and it is also valid when the network is ungrounded
(compensation coil is switched off).
In case operation direction is set to reverse, the resistive and amplitude sectors are
mirrored in the operation characteristics.
When “Amplitude” is selected, the set minimum trip current threshold is compared to the
amplitude of
I
o stab
1
. This selection can be used in ungrounded networks.
In compensated networks, setting
Operating quantity
should be set to
“Adaptive”. This enables secure and dependable directional
Section 4
1MAC059074-MB A
Protection functions
446
615 series ANSI
Technical Manual
Summary of Contents for Relion 615 series
Page 1: ... RELION PROTECTION AND CONTROL 615 series ANSI Technical Manual ...
Page 2: ......
Page 39: ...Section 17 Glossary 1181 Table of contents 615 series ANSI 33 Technical Manual ...
Page 40: ...34 ...
Page 64: ...58 ...
Page 216: ...210 ...
Page 884: ...878 ...
Page 1038: ...1032 ...
Page 1136: ...1130 ...
Page 1172: ...1166 ...
Page 1180: ...1174 ...
Page 1186: ...1180 ...
Page 1192: ...1186 ...
Page 1193: ...1187 ...
Page 1194: ......
Page 1195: ......
